private init() {
   synthesizer = AVSpeechSynthesizer()

   // Get voices for current locale
   let userLanguage = AVSpeechSynthesisVoice.currentLanguageCode()
   let list = AVSpeechSynthesisVoice.speechVoices()
   listVoices = list.filter { voice in
      return voice.language == userLanguage
   }
   // Select Ava Premium
   let voiceID = "com.apple.voice.premium.en-US.Ava"
   if let found = listVoices.first(where: { $0.identifier == voiceID }) {
      selectedVoice = found.identifier
   } else if let first = listVoices.first {
      selectedVoice = first.identifier
   }
}